1. Field of the Invention
The present invention relates to a method for the production of laminated glass panes with thermal radiation shielding properties using an interlayer film based on polyvinylacetal with a heat-shielding coating.
2. Description of the Related Art
For the production of laminated glass panes with heat shielding properties, among others, methods are customary in which thin IR-absorbing or reflecting coated PET-films are included between various layers of polyvinylacetal containing a plasticizer. It is disadvantageous that always at least 3 layers of film (1× functionalized PET, 2×PVB film) must be used, since PET can not be melted directly with the functionalized side or the backside on a glass surface.
If one does not consider different coating options of the glass surface, the alternative lies in the use of intermediate layers, which contain IR-absorber in the bulk. To this end, for example, nanoscale semiconductor particles, like ITO or ATO, are evenly distributed in the film's bulk during film production. In this case, a disadvantage lies in the limited recycling capacity of the film, which also gives rise to higher production costs. A further disadvantage lies in the difficulty of retaining the nanoscale distribution of particles in a film matrix during an extrusion process, in the presence of various other materials, in order to avoid the problem that agglomeration of nanoparticles does not give rise to an unacceptable turbidity. A further drawback lies in the higher complexity of film production, which causes, by combining the feature “heat absorbing” with further functional features like “acoustic attenuation”, “band filter”, “wedge-shaped thickness profile”, and “color hue”, a huge increase in product range for the manufacturer as well as for the processor.
As an alternative, WO 2005/059013 A1 proposes the application of heat absorbing nanoparticles by means of printing a PVB film with special print inks. However, printing can negatively affect the adhesion properties between the film and the glass surface. Due to the fact that PVB films, in order to have full removal of air during the lamination process, need to have a roughened surface, it is likely to result in an applied layer partially absorbing light even in the visible spectrum, which, after compressing with a glass surface, is optically uneven. Moreover, the printing of thick plasticized film bands is difficult, since these films elongate during unwinding, and then shrink again.